1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a storage medium. In particular, the present invention relates to an image processing technique that controls a gradation of moving images.
2. Description of the Related Art
Conventionally, various image correction techniques for controlling contrast, white balance, color balance, etc. of still image data have been proposed. One of the image correction techniques is discussed in Japanese Patent Application Laid-Open No. 11-317959 (see FIG. 9).
Japanese Patent Application Laid-Open No. 11-317959 discusses a method for checking features of an image based on a color bias ratio in a highlighted portion of the image, adjusting the degree of white balance correction in accordance with the determined features and optimizing contrast, highlights, and shadow to faithfully reproduce a color of the object.
On the other hand, such an image correction technique for correcting contrast, white balance, color balance, etc. of an image is also necessary for a moving image, similar to a still image.
However, when the above described image correction technique is applied to moving images, since the image correction method corrects an image on a frame-by-frame basis, a correction value would differ between adjacent frames, which causes a problem in that the correction value difference is perceived as a flicker (flicker of an image) by a viewer. In particular, such a change caused by the image correction occurs in a motionless portion (e.g., background) of the moving image. Thus, the change is perceived as image degradation.